1. Field of the Invention
This invention relates generally to the field of disc drive data storage devices and more particularly, but not by way of limitation, to a flexure assembly for supporting the heads used to access data on the disc surfaces.
2. Brief Description of the Prior Art
Disc drive data storage devices of the type known as "Winchester" disc drives are well known in the art. In such disc drives, one or more rigid discs coated with a magnetizable recording medium are mounted to a spindle motor for rotation at a constant high speed, and data are recorded on the disc surface in a plurality of circular, concentric tracks.
The recording and retrieval of data--also referred to as writing and reading, respectively--are accomplished using an array of read/write heads, typically one per disc surface, mounted to an actuator which moves the heads simultaneously across the disc surfaces to any desired track. The most common type of actuator in current use is the rotary voice coil actuator, which includes a voice coil motor coupled to an actuator body which is adapted to pivot about a shaft which is parallel to the spin axis of the spindle motor. The side of the actuator body opposite the voice coil motor comprises a plurality of head mounting arms, to which are mounted the flexure assemblies that support the heads in cooperative arrangement with the discs.
In disc drives of this type, the heads themselves are made up of a transducer--which accomplishes the actual read and write functions--carried in a slider body, which serves to carry the transducer and forms a self-acting hydrodynamic air bearing surface to "fly" the transducer in close proximity to the surface of the disc on a thin layer of air dragged along by the rapid spinning of the discs.
The function of the flexure assembly, which attaches the head to the actuator body for controlled movement to the tracks on the disc, is to provide a "down" force to counteract the tendency of the slider to fly upward on the air bearing, and to allow a small amount of compliance in the roll and pitch axes of the head--to compensate for minor variations in the disc surface--while maintaining a stiff support for the head in the yaw and "in-plane" axes.
Flexure assemblies of the prior art consist of four functional portions:
1) a mounting section, to attach the flexure with its associated head to the actuator; PA1 2) a flexible beam section, which applies a spring force toward the disc surface to counter the tendency of the head to rise away from the disc on its air bearing surfaces; PA1 3) a rigid beam section, which transfers the downward force of the flexible beam section to the head, and; PA1 4) a gimbal portion, which mounts the head and allows for the minor pitch and roll variations mentioned above. PA1 1) as mentioned above, the welding of the rigid beam to the gimbal introduces undesirable stresses in the materials of both components local to the welds, which can cause unacceptable variations in the mechanical behavior of the assembly; PA1 2) accurate alignment of the rigid beam and gimbal during the welding process requires expensive precision fixtures; PA1 3) stamp-forming of the tongue displacement and dimple in the gimbal introduce material stresses in the fragile gimbal; PA1 4) any desired changes in the location of the dimple require expensive non cost effective tooling changes, and; PA1 5) difficulty in determining exact dimple location.
The present invention relates primarily to a new rigid beam/gimbal combination, and, as such, the mounting and flexible beam portions of the flexure will not be discussed herein in any great detail.
In flexure assemblies from the prior art, the rigid beam section of the flexure is typically in the form of an elongated isosceles triangle with its base connected to the flexible beam portion of the flexure. The sides of the rigid beam are commonly formed out-of-plane from the main portion of the rigid beam to impart additional stiffness to the rigid beam. In such flexures, the gimbal section is typically formed of thinner material and welded to the rigid beam. This welding--frequently accomplished using lasers--results in undesirable residual stresses in the materials of the rigid beam and gimbal.
The gimbal portion of prior art flexures is typically photo-etched from 0.002 inch stainless steel stock, and includes a mounting end welded to the rigid beam as described above, and a gimbal end lying at the distal end of the rigid beam. The gimballing action is created by through-etching the gimbal to form a pair of gimbal arms at the outer edges of the gimbal and extending in parallel with the longitudinal axis of the rigid beam. The distal ends of the gimbal arms are connected by a cross member, and a "tongue", to which the slider/head assembly is adhesively attached, extends from this cross member back toward the rigid beam. The tongue is usually formed slightly out-of-plane from the remainder of the gimbal in the direction of the head, and a spherical dimple is stamped in the tongue extending away from the head. The height of this dimple is substantially the same as the out-of-plane displacement of the tongue.
When the rigid beam and gimbal are welded together, the distal end of the rigid beam contacts the top of the dimple at a single point, allowing the flexibility of the gimbal arms to provide the desired roll and pitch compliance in the attitude of the head.
This type of flexure assembly has several drawbacks:
It would, therefore, be desirable to create a flexure assembly which does not require welding of components or stamp-forming of features.